1. Field of the Invention
This invention relates to an apparatus for removing the dispersion medium in a metal or ceramic molded body formed through a plastic molding.
2. Description of the Prior Art
There is a method of manufacturing a molded body which comprises kneading a metal or ceramic powder with a dispersion medium such as plastic resin or wax under heating to obtain a compound having plasticity, and molding the compound by extrusion molding, injection molding, press molding or the like. The molded body is heated up to 400.degree. to 600.degree. C. to remove the dispersion medium by converting into gases through thermal decomposition. Thereafter, the molded body is heated in vacuo or in an atmosphere of hydrogen gas, nitrogen gas, argon gas or the like to course densification, and a sintered body is obtained.
A known apparatus used for the dewaxing method is a dewaxing furnace composed of a box shape or cylindrical shape vessel including a heater (Katsuyoshi Saito, "Fain Seramikkusu no Seikei to Yukizairyo (Molding of Fine Ceramics and Organic Materials)", page 326, published by C.M.C, 1985).
In the above conventional dewaxing method of removing the dispersion medium, a great quantity of gases is generated by the thermal decomposition of the dispersion medium, and the gases are necessarily removed from the inside of the molded body. Therefore, the temperature must be elevated slowly, and it requires about 150 hours. When the rate of temperature rise is erroneously set, defects such as cracking and expansion are generated in the molded body. The above apparatus is used for the conventional method to remove the dispersion medium by thermal decomposition, and therefore, the treatment using this apparatus has the problems of the conventional method.